Optical displacement sensor using optical fiber, and external force detecting device

Abstract

An optical displacement sensor is provided, in which an optical fiber is disposed between a light source and a light receiving means so that light emitted from the light source is conducted therethrough so as to be duly received by the light receiving means whereby a beam diameter can be controlled and a uniform intensity distribution of emitted light can be ensured without providing a pinhole aperture. Also, a six-axis force sensor incorporating such an optical displacement sensor is provided.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an optical displacement sensor and an external force detecting device, and particularly to an optical displacement sensor which detects relative displacement between a reference object and a measurement object based on displacement of a light reception position, and further to an external force detecting device which detects an external force applied to the measurement object based on a signal outputted from the optical displacement sensor.[0003]2. Description of the Related Art[0004]An external force detecting device, such as a six-axis optical force sensor, is conventionally known, in which a displacement amount of an action section to receive an external force, namely a measurement object, relative to a support section to support the action section, namely a reference object, is detected by an optical displacement sensor, and the external force received at the action section is measur...

AI Technical Summary

Benefits of technology

The present invention provides a six-axis force sensor that can control the diameter of a light beam and ensure uniform intensity distribution without the need for a pinhole aperture structure. This is achieved by using an optical displacement sensor with an optical fiber that conducts the light emitted from a light source and allows the light beam to impinge on the light receiving means with a minute diameter. The optical fiber has a smaller diffusing angle than the light source, increasing the ratio of output variation to displacement. The invention also includes a lens to condense the light emitted from the light source on the entrance facet of the optical fiber and a single-mode fiber for improved precision and reduced power consumption. Additionally, the invention provides an external force detecting device that uses multiple optical displacement sensors with different directions of displacement measurement and a shared light source to reduce power consumption and improve precision. The optical fiber has a smaller beam divergence angle than LED, allowing the light beam to be received at the light receiving face of a PD assembly with a minute diameter and increasing the output variation ratio resulting in enhanced precision of displacement detection.

Problems solved by technology

However, the aforementioned conventional optical displacement sensor, and the aforementioned six-axis force sensor (i.e., external force detecting device) incorporating the conventional optical displacement sensor has the following problems.

Such a pinhole aperture, however, requires a high accuracy of processing, and therefore invites an increased cost as well as an increased number of components.

Also, such a pinhole aperture structure inevitably reduces the amount of light to impinge on an optical sensor, and in order to compensate for reduction in the amount of light to impinge on an optical sensor, an increased current must be supplied to the LED thus inviting increased electric power consumption.

This increased electric power consumption leads to an increase of heat generation, which has influence on the amount of light emitted from the LED therefore resulting in deteriorating measurement accuracy.

And, in connection with the increased electric power consumption, since a conventional six-axis force sensor has three light sources (see FIG. 1), the problem of increase in electric power consumption is crucial.

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